Can we create a container (a library) in Eclipse and add jars by Gradle task?

It seems that the problem is that that the snakeyaml is only available on the classpath but not on the module path. Gradle (nor Buildship) has out-of-the-box support for that, but there are workarunds. You can mark a dependency as a module with the following snippet: https://github.com/donat/buildship-sample-modulepath/blob/master/build.gradle#L19-L22